Experts have met in England to help updat guidance on Vibrio spp. that can be found in seafood such as bivalve mollusks.

The meeting on Vibrio parahaemolyticus and Vibrio vulnificus was hosted by the Centre for the Environment, Fisheries and Aquaculture Science (Cefas) at its laboratory in Weymouth, Dorset, in mid-May. The center is jointly funded by the U.K. government’s Department for Environment, Food and Rural Affairs (Defra) and Food Standards Agency (FSA).

The Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO) held the Joint FAO/WHO Expert Meeting on Microbiological Risk Assessment (JEMRA) to revise the guidance which is expected to be published by the end of this year.

The event brought together 14 experts from 10 countries including Dr. Enrico Buenaventura, of Health Canada and Erin Stokes from the U.S. Centers for Disease Control and Prevention (CDC) and leader of the Cholera and Other Vibrio Illness Surveillance (COVIS) System.

Improved understanding
Rachel Hartnell, from the Cefas Weymouth Laboratory, told Food Safety News there had been a lot of developments in the area over recent years.

“There was a recognition that there had been a lot of things that have gone on in this space over a relatively short time like advances in satellite technology which enable us to monitor remotely for changes in permissive water conditions and genetics around molecular epidemiology and tracing different outbreak-related strains around the world. Also relatively basic things around the best methods to identify the pathogenic members of this group of bacteria in seafood, predominantly bivalve mollusks,” she said.

“The point of the meeting was to ensure that as the document moves towards publication it is containing the best, most up to date scientific evidence so it can be used for risk assessment. There is a clear appetite to get these risk assessments done and published quickly whilst the information within them is as up to date as it ought to be. Particularly this one because the science changes quickly, we were able to put so much more into it, lots of modelling and examples of wher the science is going.”

Development and uptake of methods such as whole genome sequencing and remote sensing meant the guidance needed revising.

“Remote sensing is using publicly available data from satellites that measure from above the surface sea water, salinity or other parameters, and through systems like the National Oceanic and Atmospheric Administration (NOAA) has,” said Hartnell.

“What we know about this particular group of bacteria is they are very sensitive to different environmental conditions. Particularly vibrio vulnificus, we know it will only grow in low salinity warmer water temperatures so what we can do with satellite data is produce risk maps available to anyone that can help inform decisions on whether or not you might harvest seafood or go into the water.”

Hartnell, also head of the recently designated FAO Reference Centre for Bivalve Mollusk Sanitation, said the technology helps actively manage risk in a way that was not possible five years ago.

“As those datasets become more sophisticated, more easily available and have better resolution then our ability to use them increases and we can back them up with verification and microbiological monitoring and target controls. So you are not spending resources on periods of the year perhaps wher you don’t need to monitor but you are targeting the higher risk parts of the season,” she said.

“Vibrios are quite unique as they are natural inhabitants of the marine environment, it’s not associated with sewage or anthropogenic impact in the same way that other foodborne risks associated with shellfish are.”

Risk mitigation
People can reduce risk of illness from oysters and mussels by cooking such food, said Hartnell.

“The risks are associated with eating raw seafood. There are places and people who want to eat raw seafood and it is predominantly raw oysters, not many people around the world eat raw mussels or clams.

“Without cooking there are other things that can be done. One of the technologies being explored, and we don’t have a lot of data on this so it is fairly speculative but biologically it should work, is taking oysters that may have been grown in an area that we know is at risk from vibrios and taking them out for a period of time into colder, higher salinity waters and there is some evidence that in parts of the U.S. wher that has been done it has had an impact.

“There are other post-harvest treatment practices which can be used such as high pressure treatment and irradiation depending on wher you are in the world. The important thing to know is when you are most at risk and be able to actively manage that risk through a range of pre and post-harvest treatment approaches.”

Vibrio spp. burden
Some species of this group, which includes the organism that causes cholera, are found naturally in warm seawater and can cause outbreaks of sickness, diarrhea and occasionally fatal septicemia.

Europe lacks complete epidemiological surveillance but a picture of the burden can be seen thanks to CDC figures. Vibriosis causes an estimated 80,000 illnesses and 100 deaths in the U.S. every year.

“The situation in Europe is quite different, wheras we do have vibrio parahaemolyticus infections we don’t see them on the size and scale that they do in the U.S,” said Hartnell.

“Vibrio vulnificus can be fatal in a high proportion of cases so it is serious but rare, we don’t see cases in Europe. Even without an epidemiological surveillance network if people were dying we would know all about it. If you get parahaemolyticus or vulnificus it is not notifiable and that is the problem.”

Hartnell said there is uncertainty but climate change is likely to have an impact as waters become warmer.

“What we do know is that incidents of illness associated with vibrio parahaemolyticus and to a lesser extent vibrio vulnificus in many different parts of the world are usually corresponding with warmer sea water temperatures. What we see with climate change is an increased frequency of climate anomalies so unusually warm years which often happen at the same time as you get unusually heavy rainfall,” she said.

“So the conditions that appear to be resulting from what we broadly call climate change are permissive for growth of these organisms. There is a good body of evidence that suggests risks will increase in certain parts of the world with warming sea temperatures.”

Jeffrey LeJeune, representing FAO and WHO, said microbial risk assessment is an approach to determine the extent that foods pose a threat to health.

“In this regard, JEMRA provides the scientific basis for development of international standards for food safety and fair practices in food trade. We are pleased to have this meeting hosted at Cefas to review and updat the risk models, so that latest advances in science and technology are leveraged to inform strategies to lower the burden of disease caused by this important group of pathogens in seafood.”

By Joe Whitworth